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ESSAY ON PEAR-BLIGHT. 



HEAD BEFORE THE 



POTOMAC FRUIT-GROWERS' ASSOCIATION, 



WASHINGTON, D. (J. 



By JEHU BRAINERD, 

TOGETHER WITH AN INTRODUCTORY NOTE BY J. P. KIRTLAND, M.D. 



COLUMBUS: 

NEVINS & MYERS, BOOK AND JOB PRINTERS. 

1876. 



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ESSAY ON PEAK-BLIGHT. 



READ BEFORE THE 



POTOMAC FRUIT-GROWERS' ASSOCIATION, 



WASHINGTON, D. C. 



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By JEHU BRAINEED, 

TOGETHEK WITH AN INTRODUCTORY NOTE BY J* P. KIRTLAND, M.D. 



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COLUMBUS: 

NEVINS & MYERS, BOOK AND JOB PRINTERS. 

1876. 



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PEAR-BLIGHT. 



[The blight in pear trees is one of those singular phenomena which 
hitherto has defied successful investigation. The following article, con- 
tributed by Prof. Brainerd (formerly a professor in the Cleveland Homoeo- 
pathic College, but during the past fifteen years occupying a very respon- 
sible and important position in the Patent Office in Washington), is so 
highly indorsed by Prof. Jared P. Kirtland, of the Cleveland Medical 
College, as to induce one to believe that if Prof. Brainerd's theory is not 
absolutely the true one, it is at all events much nearer the truth than 
any heretofore promulgated. 

There is at this moment no one in Ohio who is the peer of Prof. Kirt- 
land in vegetable physiology. During an active intellectual life, which 
has happily been extended to the full measure of four score years, he has 
been a vigilant and appreciative observer of every phenomenon of vegeta- 
ble life which presented itself to him. To his intelligence and skill are 
we indebted for several of our choicest varieties of cherries, the " Gov. 
Wood," "Kirtland's Mary," and others. His successful experiments in 
budding, grafting, inarching, and hybridizing fruits,' flowers, grapes, and 
berries are almost endless. A theory relating to diseases in the vegeta- 
ble world must, therefore, have positive merit before it can receive such 
an affirmative commendation at his hands. — Klippart.] 

PROF. KIRTLAND'S LETTER ON PEAR-TREE BLIGHT. 

East Eockport, Ohio, October 28, 1876. 
Prof. Jehu Brainerd, Washington, D. C. : 

Dear Sir: I have recently read your interesting and instructive re- 
port on "The Pear-Tree Blight." Allow me to congratulate you on 
having probably discovered the origin and nature of that malady, a mal- 
ady that has hitherto baffled the investigations of the scientific and 
practical pomologists. 

A knowledge of the pathology of a disease of the human system is 
often an important advancement towards effecting a cure or a prevention ; 
a remark equally applicable to diseases of the vegetable kingdom. 

In the summer of 1812, while pursuing the study of medicine in Hart- 
ford, Connecticut, a low and malignant fever appeared and spread ex- 
tensively in that city. Athletic soldiers in the United States canton- 
ment, as well as citizens, were frequently one hour apparently in the 



enjoyment of perfect health, and in the next sinking into the arms of 
death, perhaps before remedies could be applied. 

Coincident with the spreading of that epidemic among the human 
family, blight appeared extensively in the pear orchards. Trees were 
attacked of all ages, some dating back to provincial times, and of size 
equaling those occasionally met with at this day on the banks of the 
Detroit river, the remains of French planting in or before the times of 
Pontiac. Its attacks were as sudden as those of the sinking fever, and 
resulted suddenly in either the death of the trees or of extensive impair- 
ment. Public attention was greatly awakened by its ravages, and as 
ignorance of its cause prevailed, and in Avant of an explanatory hypoth- 
esis, the public generally concluded that it was the same pestilence which 
walketh in darkness that was alike laying its heavy hand on the people 
and the pear trees. This indefinite hypothesis prevailed for a time, till, 
in succession, it was displaced by that of insect depredation, frost impres- 
sion, and fungoid poison. Neither of these suggested any practical 
means of relief from the evil. Since that period, sixty-four years, I have 
attentively watched the progress of the blight in different and remote 
parts of our country, and noted numerous facts bearing on the subject. 
Your views seem to embrace a well-founded theory of the cause of the 
disease, which indicates appropriate methods for preventing or counter- 
acting it. More phenomena attending its rise and progress are thereby 
explained than by any or all the hypotheses hitherto advanced. I am 
happy to add that my own experience during that long interval of time, 
trivial as it may have been, sustains their correctness. If they be cor- 
rect, of which little doubt can be entertained, it is highly important 
that they should be extensively diffused among practical pomologists. 

No specific is at present known, yet evidences are not wanting that an 
energetic and persevering course of management will do much to remedy 
the evil of this disorder. The cultivator must take into consideration the 
character and selection of the variety of the fruit (Seckle and Winter 
Nellis rarely blight), the soil, and its condition in relation to drainage 
and moisture, special manures, cultivation or non-cultivation of the 
ground, shading and protection from the sun and from a south and south- 
western exposure, mulching, freeing the bodies from old and rough bark, 
and washing annually with a solution of soda ash, correct pruning of the 
season's growth in autumn, and pinching off the top of each limb before 
the formation of the terminal bud, late in June, and other items too 
numerous to mention. 

Incidentally, it may be added, that the cultivator should learn to 
gather his fruits at the moment the stem will cleave from the spur with- 



out fracture, and to ripen them in a dry room. Each individual winter 
or autumn pear must be, immediately after gathering, wrapped in a sep- 
arate paper, as oranges are preserved, and packed not over three layers 
deep, in either drawers, boxes, or crocks, placed in a dry and empty room. 
If the rind be allowed to wilt before the wrapping and packing be accom- 
plished, the fine qualities of the variety will never develop. 

Bishop Heber wrote that he found none of the East India fruits as 
palatable as those of temperate Europe. A Baron de Anjou, Dix, Lycur- 
gus, or Winter Nellis, thus ripened, will favorably compare with the 
orange, guava, and pine apple of the tropics. Much is yet to be learned 
in the art and science of pear culture. 

Very respectfully yours, 

Jared P. Kirtland. 



REPORT ON THE BLIGHT OF THE PEAR TREE. » 

BY PROF. J. BRAINEUD. 

So far as I am able to learn, there is no settled theory in regard to the 
cause of the Pear-Tree Blight, and to my mind the discussion of subjects 
not definitely established accords perfectly with the ruling spirit of this 
Association, and when they are carefully considered can scarcely fail of 
some good results. 

If our extreme modesty forbids the approach of such subjects, may it 
not be said that we fall short in the first and foremost object for which we 
are associated ? 

In order to comprehend the full significance of these observations, it 
will be necessary to call to mind some facts regarding the structure of 
plants and trees, and the phenomenon of the circulation of the sap. 

In what is called saji-wood there is laid up in &tore soluble matter des- 
tined to contribute to the future development of the tree. This is clearly 
shown in the sugar-maple (acer saccharinum) , and a knowledge of this fact 
is made available for obtaining a delicious sweet. 

Sap is essentially a watery fluid, which the roots absorb from the earth, 
and contains or holds in solution a minute quantity of carbonic acid and 
ammonia and a few mineral constituents, drawn from the soil in a con- 
dition of solution in water. 

In its ascending course, through the cells of the sap-wood, it meet 
with and dissolves a portion of the soluble cell-contents, and thus becomes 

a Read before the Potomac Fruit-Growers' Association, Washington, D. C., September 

5, 1876. 



6 

more and more dense as it approaches the bud where it is appropriated 
to the development of the leaf, in which it undergoes a futher elaboration, 
and returns upon the outside of the sap-wood, to form a new growth, and 
in this condition is called alburnum. 

In "Rhind's Vegetable Kingdom" this matter of sap circulation is fully 
examined. In this and other standard works on botany the fact that the 
ascending sap in exogenous trees passes upward through the growth of 
the previous years (hence called the sap-wood) is so universally admitted 
that its discussion here would be out of place. 

The alburnum, then, is the layer or growth of the present year, that 
will form the sap-wood of the succeeding year. And this sap-wood may 
continue in activity for a number of years, and until the cells which form 
its structure become filled with mineral deposits, thereby becoming heart- 
wood and of no further use, so far as the vitality of the tree is concerned. 
It is, however, of value in giving strength to sustain the accumulating 
weight of the growth, but the vitality of the tree would not be affected 
by its removal. 

Before I call attention to the sketches I have made, from microscopic 
examinations of the specimens submitted for that purpose at the August 
meeting, and since procured, it will be proper to examine, briefly, the 
anatomy of the growth under consideration. 

The sap-wood is made up essentially of elongated cells, either joined 
end to end, or overlapping each other. During the growing season these 
cells are filled with crude sap of constantly increasing density from the 
spongiole of the root, where it is little else than water, to the extremity 
of the highest leaf. 

In the leaf system it becomes elaborated sap, fitted for the formation, 
in its descent, of a system of new cells between the bark and the last 
year's growth, and which, when in the act of forming, is called alburnum, 
as before stated. 

It is owing to the extreme delicacy and tenderness of these forming cells 
in the spring of the year that we, in our boyhood days, were enabled to 
make our "toy whistle of bark." 

I will now call your attention to the possible causes of blight, and pro- 
ceed to examine the sketches I have made from actual views under the 
microscope. 

In an English work on " Practical and Scientific Fruit Culture, by 
Charles R. Baker," pages 420, 421 , we find this significant statement : " That 
the enlargement of the flesh of a fruit, the entire or partial absence of 
seeds, are the result of disease, strictly considered; and yet these conditions 
are very desirable in fruit culture." 



What we are to understand by the term disease, in this statement, must 
be held to relate wholly to the vitality of the tree, for it is a well-known 
fact that in fruits, as well as in animals, an excessive development in 
any particular direction — the fostering of favorite qualities — weakens 
the power of resistance against the vicissitudes of climate and the nu- 
merous natural foes to longevity, producing what may properly be termed 
an ancemic condition of the tree. 

Fig. l. 




NATURAL SIZE— SOUND BRANCH, AND SAME BLIGHTED. 

When I entered upon this examination, I was inclined to attribute the 
blight to the depredations of some species of insects, but I determined to 
conduct the investigation without bias ; I could not, however, pass over 
this point without due consideration. 



8 

I therefore made diligent search for evidences of this character, but 
found none, with the exception of two or three spurs in perhaps fifty ex- 
amined, in which appeared slight evidences of the work of the Pear- 
Blight Beetle, Scolytus pyri. This insect, which is very small, causes a 
blight of spurs and small twigs, which, in its outward appearance, resem- 
bles the common pear-tree blight. 

The limbs or spurs attacked turn black and die, while other parts of 
the tree remain healthy. The egg of the insect is laid in the axil of the 
bud; the larva eats its way inward through the alburnum, and forms a 
circular passage in the sap-wood, thus cutting off the vessels for the as- 
cending sap; the whole part above, being deprived of nutriment, dies. 

I am satisfied, from a most careful examination, that the kind of blight 
under investigation is not caused by this nor any other insect, for I failed 
to find either the grub or the conditions above stated. 

Since writing the foregoing paragraph, I have succeeded in finding the 
living larva of two individual specimens of Scolytus pyri. The branches 




NATURAL SIZE — LARVAE OF THE SCOLYTUS PYRI, MAGNIFIED TWENTY DIAMETERS. 

had been in my possession about ten or twelve days. At this stage of 
their development their length is about one-tenth of an inch, a reddish 
brown head, two short hooked mandibles, dark eyes, large thorax, fifteen 
articulations, two or three stiff hairs upon the sides at each articulation, 
body very light straw color, almost white, and semi-transparent. The 
point where the larva entered the bark is scarcely perceptible without a 
magnifying glass, appearing not larger than a puncture made with the 
point of a needle. Their course is first inward, toward the pith from the 
base of the spurs, thence downward along that soft tissue. The discovery 
of these living larva should not be taken as evidence of a cause of the 
blight, inasmuch as their development was subsequent to the blight. 

That the egg of the insect was deposited previously to, or about the 
time of the occurrence of, the blight is quite probable, but the tree had 
sustained no injury from the larva at that time. 

We must, therefore, look for other causes, and in doing this we can 
have no more reliable guide than the revelations of the microscope. 

I next turned my attention to the discovery, if possible, of a fungoid 
growth, by many regarded as the cause of blight. But, upon the closest 



9 



scrutiny, no evidence of this character appeared. I am, therefore, forced 
to the conclusion that fungus, whenever it does appear, is the consequence, 
and not the cause, of blight. 



Fig. 2. 



Fig. 3. 




a. Pith. b. Sap-wood. c. Alburnum. 
NOT BLIGHTED. BLIGHTED BRANCH. 

' (Both magnified two diameters.) 

I now call your attention to the microscopic views which I have pre- 
pared with scrupulous fidelity to the specimens before me. 

Figure 1 shows a healthy and a blighted branch. 

Figure 2 shows cross and longitudinal sections of the healthy branch 
magnified. 

Figure 3 shows a like view from a blighted branch. 

Figure 4 shows a slightly magnified branch blighted twenty-four hours 
previous to examination. The entire growth above the blighted portion 
was green and vigorous, showing a continuous supply of ascending sajj, 
while the bark and alburnum in the blighted portion was dark and with- 
ered. 

Figure -5 shows magnified vertical sections of health}' and blighted 
branches. 

Figure 6 shows magnified views of stomata, in the green bark of the 
young shoot, both natural and blighted, with cross-section of the same. 

In these examinations but one conclusion can be entertained, and that 
is, that the newty formed cells in the alburnum have, from some cause, 
been ruptured, and the elaborated sap, destined for the support of the 
fruit and the perfecting of the new growth of wood, poured out into the 
interspaces of the cells, coagulated and disorganized, producing in the 



10 

vegetable tissue a condition analagous to what is termed extravasation of 
blood in the animal tissue. 

A comparison of the healthy alburnum with that struck with the 
blight shows most clearly that this statement is fully borne out by the 
facts in the case. 

The microscopic appearance of the coagulated sap in the blighted por- 
tions of the stem, under a high magnifying power, was most remarkable. 

Every vestige of cell formation was destroyed, and nothing could be 
seen but a dark coagulated mass, pushed out in rough masses through 
fissures in the bark ; and this appearance extended through the whole 
thickness of the alburnum, while the sap-wood remained in a perfectly 
healthy state, conveying sap to the unblighted portions above, as seen 
in figure 4. The color of this coagulated sap presented all shades, from 
a pearly luster to a dark brown, presenting many irregularities and cav- 
ities, caused by contraction from loss of watery fluid. 

The external bark and leaves appeared as though they had been 
scorched in a fire; hence the disease is aptly called " Fire Blight." 

There are two causes that produce the rupture and destruction of newly 
formed cells in the alburnum, and the action is very sudden and certain. 
These are extremes of heat and cold. In the spring of 1875, in Ohio and 
along the lake shore fruit region, after the trees had put forth their 
leaves, a sudden fall of temperature from summer heat to twelve or fifteen 
degrees below freezing killed outright nearly every pear tree in that ex- 
tensive fruit district. 

I examined many trees soon thereafter, and found the external ap- 
pearances exactly similar to what is called the " Fire Blight;" that is, the 
trees had the appearance of having been roasted in an oven. 

The green and tender portions of the tree, especially the alburnum, 
are made up of cells whose membranous walls are very thin and delicate, 
and when the sap with which these cells are always filled is subjected 
to sudden expansion, from either high or low temperature, the cell-walls 
become ruptured, and the sap, of course, runs out and is diffused among 
the tissues, and its nutritive action is lost. 

A putrefactive condition soon follows, giving rise to fungoid growth, 
if other conditions are favorable. 

In order to test thoroughly the influence of heat, I subjected a vigorous 
and healthy branch of a pear tree to an artificial heat of 108 degrees Fah. 
for twenty minutes. The effect upon the leaves and soft tissues was ex- 
actly like that of the natural blight. 

The normal heat for the fruit-producing season ranges from 65 degrees 
to 85 degrees Fah., the mean of which is 70 degrees. 



11 



A temperature of 95 degrees is dangerous, and 100 degrees to 108 degrees 
is disastrous. 

Fig. 4. 



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BLIGHTED BRANCH, SHOWING HEALTHY SAP-WOOD, GIVING SAP TO UPPER BRANCHES. 

A curious fact has been observed, and thus far not accounted for, and 
that is, the tendency of the blight to go in streaks through the orchard 
or nursery, sometimes being confined to a belt of a few feet in diameter, 
and the course of the blasting current of hot air is generally at right 
angles with the direct rays of the sun. 

For example, if the injury is sustained in the afternoon, the]direction 
of the wave will be from north of west to south of east. (Baker.) 

The alburnum, or forming wood, being made up of cells exactly like 
those of the sap-wood, but tender and delicate in structure, when becom- 
ing gorged with sap from excessively favorable conditions of growh 
possess not the power to resist the pressure of the expanding sap under an 
almost tropical solar heat, oftentimes increased in intensity by the situ- 
ation of the ground. 

From careful observation and inquiry, I have found that orchards, or 
single trees, upon a southern exposure are much more liable to the blight 
than those on northern exposures. 

As corroborative of this, I will state that I have seventy-five pear trees 



12 



in Prince George's county, Maryland (Duchess and Bartlett), now six years 
old, on a northern exposure; none of them are blighted. 

Dr. Palmer, of this city, has an orchard of about forty pear trees, about 
two miles north of the boundary line, on the Bladensburg road, on a 
northern exposure, and no blight has touched them, while half a dozen 
trees on a southern slope of the land, upon the same farm, have been 
completely destroyed by the blight. 

Dr. Breed had pear trees on a southern aspect, and they were all affected 
with the blight. He removed them to ground sloping toward the north, 
and they soon became healthy, fruitful, and no blight has since touched 
them. 

Newton Crawford, Esq., of Bladensburg, has pear trees on ground fac- 
ing the south ; they are all ruined this year by the blight. 

Mr. Throckmorton, of Virginia, about the tenth of August, brought 
me branches of a pear tree, in full bearing, which had been planted in a 
hollow left in leveling an old fort, where it was exposed to excessive heat, 
with water standing about its roots after a heavy rain. The tree flour- 
ished in the early part of the season, and on the first week in August was 
in a fine condition and full of fruit. It was struck with blight on one of 
the hottest days, about the fifth of the month, and in two days was com- 
pletely withered. Other pear trees of the same age, standing on the 
northern side of the hill remain in full vigor to this day. 

Fig. 5.— Longitudinal Sections. 



It r '^""'7 'i \ 'a \ 



/ 



if/ 




a. Alburnum. 
NOT BLIGI1TKD. 




b. Sap-wood. 



13 

Besides these instances, many others might be given, extending over 
a wide range of country, but these, it must be admitted, tend strongly 
to confirm our theory. 

By reference to "Rhind's Vegetable Kingdom," it will be seen that 
the pear tree is indigenous to the northern sections of the temperate zone, 
flourishing in its native forests, as far north as fifty-seven degrees of 
latitude. 

It seems to delight in a northern aspect, or at least is most hardy and 
long-lived when growing in positions where it is protected from intense 
solar heat. 

In attempting to acclimate it to a warmer climate, its primitive habits 
should be regarded, and situations selected for its growth that will most 
promote its successful cultivation. 

In the culture of fruit of any kind that is subject to maladies, and 
especially to fatal ones, which so often blast the hopes of the fruit-grower, 
it should be the first object to discover the cause, and then there is a bet- 
ter prospoct of being able to find and appl} 7 a remedy. 

It is undoubtedly true that grafting upon seedling stocks, raised from 
the seeds of highly cultivated fruit, greatly weakens the vitality of the 
tree ; that is, the stock is feeble, and the roots do not strike vigorously 
into the soil, and when, by reason of the excessive demand for material 
to supply the requisite pabulum for the development of the choicest fruit, 
the roots soon become inadequate to^furnish that supply, and a failure is 
the inevitable consequence ; and, besides, a sickly tree, although planted 
in a favorable situation, is much less able to withstand the attack of an 
enemy than one in vigorous health. 

Another evil we have to contend with is deep cultivation around the 
roots of the growing tree. 

The roots of the pear tree, especially those highly cultivated, run near 
the surface of the ground. Deep plowing around the tree cuts off the 
roots that supply nourishment. 

In a recent conversation with Mr. Munsell, a successful fruit grower of 
Chardon, Ohio, I learned that he has greatly improved his pear trees, 
smitten with the blight, by carefully digging about the roots, taking 
care not to injure them, and mulching with mineral coal ashes and broken 
bones, mixed with good soil, at the same time digging a deep trench 
around the trees at the extremity of the roots, for the purpose of drain- 
age and filling it with broken bones and coal ashes. Trees thus treated 
became health}' and fruitful. 

Their situation was on high ground, nearl} r level, clay soil ; the general 
slope of the land north, toward Lake Erie. 



14 

Fruit trees, to become vigorous and fruitful, must have the conditions, 
soil, and culture necessary to their successful development. 

Fig. 6. 




d. Stomata. e. Young t-wij;. 

NATURAL, STOMATA. BLIGHTED STOMATA, FOUR DIAMETERS. 




Neither the forming tissues of the wood nor the substance of the fruit 
can become perfect unless the carbon, hydrogen, nitrogen, sulphur, phos- 
phorus, alkalies, and other elements are liberally supplied to the roots in 
due proportions and conditions fitted for absorption. 

To insure a healthy growth and fruitage, and at the same time guard 
against the blight and other diseases to which the pear tree is subject, 
certain sanitary measures must be observed. 

The most important of these is situation. A north or north-east slope 
of land is the most favorable, all other things being equal, for the reason 
that the solar heat culminates an hour or two after meridian, usually 
from one to two o'clock in the afternoon. 

Deep cultivation and underdrainage before planting the trees should 
be secured. For pear trees a deep, loamy soil, with abundant moisture, 
but not an excess, is to be preferred. Top-dressing, with proper fertilizers, 
especially finely broken or ground limestone, should be freely used around 
the trees, as far as the roots extend. 

Grafts from young, vigorous, bearing trees should be set upon the native 
crab or thorn. This will secure a strong and healthy root-growth ; thus 
securing a constant and full supply of food from the commissary depart- 
ment of the tree. A horse would not thrive if stabled in a quagmire, and 
fed only upon ferns and sedge-grass. No amount of physic or grooming 



15 

would supply his natural wants. He must have good conditions and 
food. So with pear trees. If they are unfavorably located in an insuffi- 
cient soil, with an aspect inviting destruction by the blight, all the sulphur 
and lime baths, whale oil soap-suds washes, and linseed oil liniments that 
can be applied will not save them. 

All the therapeutic agents in the world will not bring to the tree the 
necessary conditions of health, prosperity, and usefulness. 

In conclusion, I will remark that the evidences, to my mind, are con- 
clusive that the blight of the pear tree is caused wholly by excessive 
solar heat, by which the tender and forming cells are ruptured, the elab- 
orated sap poured out into the disorganized tissues, coagulated and dried, 
and consequently rendered unfit for the purposes of nutrition and growth. 

And I believe that it will be found, upon further investigation, that 
the sections of the branches smitten have not been protected by foliage 
from the direct rays of the sun, while portions above the affected part, 
protected by leaves, have not been injured, but necessarily soon die from 
secondary causes. 

If this hypothesis of pear-tree blight be the true one — and the accumu- 
lating evidence assuredly does point in that direction — then the remedy 
for this great evil must be sought, not in external applications to the in- 
jured parts, nor even by excision, but by planting in suitable soil, and in 
situations that will afford protection from the devouring heat. 



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